1. Field of the Invention
The present invention relates to a polishing apparatus and a polishing method of polishing a surface of an optical member or a substrate by spraying a fluid or an abrasive suspension thereto, a control program for causing a computer to execute polishing, and a recording medium.
2. Description of the Related Art
Conventionally, a technique for polishing a surface of an optical member or substrate by the jet of a fluid or abrasive suspension is disclosed.
For example, Jpn. Pat. Appln. KOKAI Publication No. 5-57591 discloses the following technique. A lens is held by the pressure of a polishing solution jetted out from large numbers of holes in tools arranged above and under the lens. The two surfaces of the lens are entirely polished simultaneously by rotating the jet ports of the polishing solution and the lens relative to each other. According to the technique disclosed in Jpn. Pat. Appln. KOKAI Publication No. 5-57591, however, the two surfaces of the lens are polished entirely. It is impossible to select only part of the lens and polish only the selected part.
Jpn. Pat. Appln. KOKAI Publication No. 5-201737 discloses the following technique. Cutting of a glass sheet and polishing of the cut glass edge are performed by using a jet solution of an abrasive suspended in water. In this manner, according to the technique disclosed in Jpn. Pat. Appln. KOKAI Publication No. 5-201737, cutting and grinding of the cut surface are performed by jetting out to the glass sheet a jet solution suspended with the abrasive. Thus, a tool for jetting out the jet solution jets out the jet solution while moving parallel to and perpendicularly to the glass sheet surface. With this technique, a surface having a concave or convex as in an optical lens cannot be polished. Also, Jpn. Pat. Appln. KOKAI Publication No. 5-201737 does not disclose any means that changes the jetting direction of the jet.
U.S. Pat. No. 5,951,369 discloses the following technique. A flange attached with a polishing solution suspended with magnetic abrasive particles is rotated. This changes the strength of the magnetic field at a polishing portion. Thus, the concentration of the magnetic abrasive particles is changed, so that the polishing amount is controlled. According to the technique disclosed in U.S. Pat. No. 5,951,369, the polishing solution suspended with the magnetic abrasive particles is attached to the periphery of the flange, and the flange is brought into contact with a polishing zone, so that polishing limited to the contact zone is enabled. With this method, the polishing amount can be changed in accordance with the strength of the magnetic field. The polishing amount also changes largely in accordance with the urging force of the flange against the polishing zone. The relationship between the urging force and adjustment of the polishing amount, however, is not disclosed. Hence, it is difficult to finely adjust the polishing amount of the polishing zone.
U.S. Pat. No. 5,971,835 discloses the following technique. While a fluid suspended with magnetic abrasive particles is sprayed to a rotating workpiece, the spraying direction is controlled by a solenoid. The polishing position is thus adjusted. According to the technique disclosed in U.S. Pat. No. 5,971,835, the change amount of the fluid spraying direction against the workpiece is very small. Accordingly, it is difficult to spray a solution to an uneven surface, that changes largely in the direction of normal to the work surface, perpendicularly or at a constant angle.